The present invention relates to an apparatus for cooling, stabilizing and preparing melt-spun filaments.
A known apparatus for cooling, stabilizing and preparing melt-spun filaments includes means for making an annular bundle of melt-spun filaments, a blowing air dispensing means arranged in the center of the annular bundle of melt-spun filaments and a preparation application device for applying a preparation to the filaments.
Swiss Patent CH-A-667,676 discloses a porous blowing air dispensing means which is positionable in the center of an annular bundle of filaments downstream of a melt jet and which feeds gas radially symmetrically through the bundle of filaments from the interior of the bundle to the exterior. In this way, the heat from the melt jet is efficiently removed from the filaments. A preparation can thus be applied directly to the filaments underneath the blowing air dispensing means and the filaments can then be combined to form a closed bundle. Adhesions between the individual filaments do not occur.
It has, however, been shown that this known apparatus cannot be used for all cases. When spinning multifilament yarns, for example yarns made of polyethylene terephthalate (PET), with relatively high individual filament denier, in particular at spinning speeds of 2000 m/min and more, yarns are obtained which cannot be further processed in the conventional manner, in particular stretched. The stretching process is disturbed so much by the occurrence of an intolerable number of filament breakages that a yarn with adequate mechanical properties cannot be produced.
It has been shown that the multifilament yarns spun in this way have very great irregularities in their molecular structure. The values determined for the optical birefringence, as a measure of the molecular orientation, are subject to unusually great variations, both from filament to filament and along the individual filaments, and in each case cover a very wide range.
However, the requirement for regularity of continuous multifilament yarn is so high that, for example, in the case of filaments of polyethylene terephthalate, values for optical birefringence should not vary by more than 10% of the measured mean value. When stretching filaments which have more than a 10% variation in birefringence, an intolerable number of filament breakages is indicated. Moreover, such irregular filaments when present in textiles cause unsatisfactory color intensity variations during dyeing of the textiles.